Ethernet LAN Module 5 Quiz

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Questions and Answers

What is the main purpose of the preamble in an Ethernet frame?

Detects corrupted data in the frame

Indicates the type of the encapsulated packet

Marks the end of the frame

Allows devices to synchronize their receiver clocks (correct)

What does a Frame Check Sequence (FCS) do?

Specifies the type of encapsulated packet

Synchronizes the receiver clocks

Indicates the source MAC address

Detects corrupted data using a Cyclic Redundancy Check (correct)

Which value in the type field of an Ethernet frame indicates that the length of the encapsulated packets is specified?

A value less than 1500 (correct)

A value equal to 1500

A value equal to 1536

A value greater than 1536

What is the format of the MAC address used in Ethernet frames?

6 bytes in length Signup and view all the answers

What is the total byte size of an Ethernet frame including its header and trailer?

26 bytes Signup and view all the answers

What hex value indicates an encapsulated IPv4 packet in the type field?

0x0800 Signup and view all the answers

What does the Start Frame Delimiter (SFD) signify in an Ethernet frame?

The end of the preamble Signup and view all the answers

What is the function of the destination address in an Ethernet frame?

Identifies the device receiving the frame Signup and view all the answers

What type of message is used by a device to request the MAC address of another device?

ARP Request Signup and view all the answers

What is the primary purpose of a MAC address?

To provide a unique identifier for networking devices Signup and view all the answers

Which statement is true about the ARP Reply message?

It is sent only to the host that made the request. Signup and view all the answers

What does the command 'arp -a' do?

Displays the ARP table entries. Signup and view all the answers

Which of the following formats represents a MAC address correctly for Cisco devices?

0011.5ccc.5c00 Signup and view all the answers

What is the role of the Organizationally Unique Identifier (OUI) in a MAC address?

It identifies the specific device manufacturer Signup and view all the answers

When using the ping command, which two messages are exchanged?

ICMP Echo Request and ICMP Echo Reply Signup and view all the answers

What happens to dynamic MAC addresses in a MAC address table after 5 minutes of inactivity?

They are removed from the table. Signup and view all the answers

What is a characteristic of half duplex communication?

Data can only be sent or received at one time. Signup and view all the answers

What is the minimum payload size for an Ethernet frame if the header and trailer total 18 bytes?

46 bytes Signup and view all the answers

What state do router interfaces have by default due to the shutdown command?

Administratively down/Down Signup and view all the answers

Which entry type in the ARP table indicates an address learned dynamically?

Dynamic Signup and view all the answers

Which type of frame is specifically intended for communication with a single target device?

Unicast frame Signup and view all the answers

What information is found in the MAC address table of a switch?

The MAC addresses linked to specific interfaces Signup and view all the answers

Which option describes MAC Address Tables in relation to ARP?

They store mappings of MAC addresses learned from ARP requests. Signup and view all the answers

What occurs when an Ethernet frame is considered an unknown unicast?

It is flooded to all interfaces except the source. Signup and view all the answers

What is a characteristic of devices connected to a hub?

They operate in half duplex. Signup and view all the answers

What is the purpose of the jamming signal in CSMA/CD?

To notify other devices of a collision. Signup and view all the answers

What happens during speed/duplex autonegotiation?

Devices advertise their capabilities to determine the best settings. Signup and view all the answers

What will occur if autonegotiation is disabled on a device connected to a switch?

The switch will use the slowest supported speed if it cannot sense the device speed. Signup and view all the answers

Which of the following defines a 'giant' frame?

A frame larger than 1518 bytes. Signup and view all the answers

Which type of error is characterized by frames that are smaller than the minimum size?

Runts. Signup and view all the answers

What is indicated by an output error on a switch?

Frames the switch tried to send but failed due to an error. Signup and view all the answers

Which Ethernet speed supports the highest capacity among the following options?

10/100/1000 megabits per second. Signup and view all the answers

Study Notes

Ethernet Frame Structure

Ethernet frames consist of a header, payload (packet), and trailer, with a total of 26 bytes (4 bytes for FCS, 7 bytes for preamble, 1 byte for SFD, 6 bytes for destination MAC, 6 bytes for source MAC, and 2 bytes for the type/length).

Preamble and Start Frame Delimiter (SFD)

The preamble is 7 bytes of alternating 1s and 0s (10101010 * 7) enabling device synchronization.
SFD is 1 byte (10101011), marking the end of the preamble and the start of the frame.

MAC Addresses

MAC addresses are 6 bytes (48 bits) long and uniquely assigned to devices (also known as Burned-In Addresses).
First 3 bytes are the Organizational Unique Identifier (OUI), assigned to manufacturers.
Different formatting examples include:
- Windows: 5C-23-5A-24-2B-3D
- Cisco devices: 0011.5CCC.5C00
- Linux and IOS: 5C:23:5A:24:2B:3D

Type/Length Field

This 2-byte field indicates either the length of the encapsulated packet (if ≤ 1500) or its type (if ≥ 1536) with IPv4 and IPv6 specified as 0x0800 and 0x86DD respectively.

Frame Check Sequence (FCS)

The FCS field is 4 bytes long and employs a Cyclic Redundancy Check (CRC) algorithm to detect data corruption.

Ethernet Frame Minimum and Maximum Sizes

Minimum Ethernet frame size (header + payload + trailer) is 64 bytes, requiring a minimum payload of 46 bytes.
If the payload is less than 46 bytes, padding bytes are added.

Address Resolution Protocol (ARP)

ARP facilitates discovering a device's MAC address based on its known IP address, utilizing two message types: ARP Request (broadcast) and ARP Reply (unicast).
ARP tables can be viewed using arp -a in the command prompt, showing dynamic and static entries.

Ping Utility

Ping tests network reachability between devices and measures round-trip time using ICMP Echo Request and Echo Reply messages.

Switch Interfaces and CLI Commands

Switch interfaces are in an up/up state by default if connected, while router interfaces are down by default until activated.
Common commands include show ip int br to check interface status.

Duplex Modes

Half duplex allows either sending or receiving at one time, required by devices connected to hubs.
Full duplex enables simultaneous sending and receiving, commonly utilized in switch configurations.

CSMA/CD Protocol

Carrier Sense Multiple Access with Collision Detection (CSMA/CD) allows devices to listen for traffic before transmitting to prevent collisions.
On collision, devices send a jamming signal and wait a random time before trying again.

Speed/Duplex Autonegotiation

Switch interfaces default to auto settings for both speed and duplex; speeds include 10 (E), 100 (F), and 1000 (G) Mbps.
If autonegotiation is disabled, the switch defaults to the slowest supported speed.

Interface Errors

Common frame errors include:
- Runts: Frames smaller than 64 bytes.
- Giants: Frames larger than 1518 bytes.
- CRC: Failed frames based on FCS.
- Input and output errors indicating frame processing issues.

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Description

Test your knowledge on Ethernet LAN concepts as outlined in Module 5. This quiz covers topics such as switching, Ethernet frames, and the structure of data packets. Prepare to dive into the essential components that form the backbone of local area networks.